Review on Dynamic Contour Tonometry and Ocular Pulse Amplitude

Abstract

Intraocular pressure (IOP) measurement is the cornerstone of the management of glaucoma patients. The gold standard for assessing IOP is Goldmann applanation tonometry (GAT). Recently, the dynamic contour tonometer (DCT) has become available. While both devices provide reliable IOP measurements, the results are not interchangeable. DCT has the advantage of measuring an additional parameter: ocular pulse amplitude (OPA). OPA is defined as the difference between systolic and diastolic IOP and represents the pulsatile wave front produced by the varying amount of blood in the eye during the cardiac cycle. It has been shown to vary with ocular structural parameters, such as axial length, corneal thickness, and ocular rigidity, as well as with systemic variables like heart rate, blood pressure, and left ventricular ejection fraction. Although the existence of some of these associations is still controversial, the clinical relevance of OPA has been consistently suggested, especially in glaucoma. Further research on this intriguing parameter could not only provide insight into glaucoma pathophysiology but also help integrate this variable into clinical practice.

Modeling the Origin of the Ocular Pulse and Its Impact on the Optic Nerve Head

“…1 DCT is a relatively new technology for noninvasive IOP measurement using the principle of ''contour matching,'' which is less dependent on the effect of individual corneal properties. 37 Similarly, our choroidal thickness changes (7.4 lm) were consistent with those observed experimentally (16.7 6 10.9 lm). 34 To the best of our knowledge, while several models of the ONH have been proposed, 12,14,15,18,38,39 none have yet reproduced both choroidal expansion and the OPA.…”

Evaluation of ocular pulse amplitude in patients with carotid artery stenosis using the Pascal dynamic contour tonometer

“…Pascal DCT measures IOP in a continuous way and provides a pressure curve during the cardiac cycle. The difference between the systolic and diastolic IOP measurements represents the OPA value . The Pascal DCT has a liquid crystal screen on which the measured IOP value, a score for the quality of the measurement and the OPA value, are displayed.…”

“…Therefore, it can be expected that in patients with CAS, OPA tends to be lower. The Pascal dynamic contour tonometer (DCT) (Swiss Microtechnology AG, Port, Switzerland) is a new slitlamp‐mounted contact tonometer that measures both IOP and OPA simultaneously and continuously in a non‐invasive manner …”

Exercise-Induced Changes in Ocular Blood Flow Parameters in Primary Open-Angle Glaucoma Patients

“…The OPA is defined as the difference between diastolic and systolic IOP, and its magnitude seems to be related choroidal blood flow. More details about OPA and OPP can be found elsewhere [8,34,35].…”